Alignment Procedure Used in the BIPM Watt Balance de Mirandés, E; Hao Fang; Kiss, A ...
IEEE transactions on instrumentation and measurement,
2011-July, 2011-07-00, 20110701, Letnik:
60, Številka:
7
Journal Article
Recenzirano
The Bureau International des Poids et Mesures (BIPM) is developing a watt balance to measure accurately the Planck constant h by linking it to the kilogram. The kilogram is currently the only base ...unit of the International System of Units still defined by a material artifact. A fixed numerical value of h could be the basis for the expected future redefinition of the kilogram in terms of fundamental constants. One main concern of the watt balance experiment is the alignment of the involved vectors. In particular, the electromagnetic force exerted on the watt balance coil needs to be carefully aligned parallel to the gravitational force exerted on the test mass. To address this requirement, we have developed an original experimental procedure that has been validated with a test coil which is a prototype for the ultimate watt balance coil. The result is accurate enough to enable a determination of the Planck constant with a relative uncertainty of about 1·10 -8 , which is the ultimate goal of the BIPM watt balance.
Progress on the BIPM Watt Balance Picard, A.; Hao Fang; Kiss, A. ...
IEEE transactions on instrumentation and measurement,
04/2009, Letnik:
58, Številka:
4
Journal Article
Recenzirano
Since beginning the construction early in 2005, considerable progress has been made on the watt balance of the Bureau International des Poids et Mesures (BIPM). We have continued the development of a ...room-temperature version to test the feasibility of simultaneous force and velocity measurements. Preliminary measurements of the voltage-velocity ratio have been carried out with a reproducibility of the order of 1 part in 10 4 . The coil suspension has been improved to reduce the undesired coil movement in the 5 degrees of freedom different from a perfectly vertical movement. Further work on the current source has reduced its long-term drift to a few parts in 10 9 per minute with a satisfactory short-term stability. A technique needed to separate the voltage induced in the coil from the voltage drop due to the current flow based on the use of a second noninductive coil has been tested. The second coil is now being integrated into the apparatus. Work has started on the geometrical and magnetic characterizations of a large precision solenoid that will become the reference for the magnetic field alignment. The collaboration with a university on the fabrication of our magnetic circuit is being continued. This paper briefly outlines the main ideas of the BIPM watt balance and reports the progress to date.
On 16 November 2018 a revision of the International System of Units (the SI) was agreed by the General Conference on Weights and Measures. The definitions of the base units were presented in a new ...format that highlighted the link between each unit and a defined value of an associated constant. The physical concepts underlying the definitions of the kilogram, the ampere, the kelvin and the mole have been changed. The new definition of the kilogram is of particular importance because it eliminated the last definition referring to an artefact. In this way, the new definitions use the rules of nature to create the rules of measurement and tie measurements at the atomic and quantum scales to those at the macroscopic level. The new definitions do not prescribe particular realization methods and hence will allow the development of new and more accurate measurement techniques.
We present a review of the most precise determinations of the fine structure constant α which are obtained in different domains of physics. We describe the measurement of the ratio h/mRb between the ...Planck constant and the mass of Rubidium atom which leads to a precise value of α which is very few dependent of the QED. Finally, we present a review of the different determinations of the von Klitzing constant RK.
We present the recent progress on the BIPM (Bureau International des Poids et Mesures) watt balance. The existing apparatus was transferred to the dedicated new laboratory with better thermal and ...vibrational conditions. The apparatus is fully operational in air. An improvement by a factor of three was achieved on the S/N ratio of both the voltage-to-velocity and force-to-current ratios. The fabrication of the parts of the new magnet is completed and its assembly is finished.
In 2014 the Bureau International des Poids et Mesures (BIPM) carried out a calibration campaign using the international prototype of the kilogram (IPK). This is the second part in a series of ...publications describing the results of that campaign. As reported (Metrologia 52 310-6), following the comparisons between the IPK and its official copies, it was found that the BIPM 'as-maintained mass unit' was offset by 35 μg from the mass of the IPK in 2014. We report here the results of an investigation into this offset that has considered all data available from internal BIPM mass comparisons carried out between 1992 and 2014. This has enabled us to model the evolution of the offset in the as-maintained mass unit and to identify some possible reasons why it has developed. We also report how the model has been used to estimate corrections to all 1 kg mass calibration certificates issued by the BIPM during this period.
In this paper we present a short overview of atom interferometry based on light pulses. We discuss different implementations and their applications for high precision measurements. We will focus on ...the determination of the ratio
h
/
m
of the Planck constant to an atomic mass. The measurement of this quantity is performed by combining Bloch oscillations of atoms in a moving optical lattice with a Ramsey-Bordé interferometer.
We present a review of the most precise determinations of the fine structure constant alpha which are obtained in different domains of physics. We describe the measurement of the ratio h/m sub(Rb ...between the Planck constant and the mass of Rubidium atom which leads to a precise value of alpha which is very few dependent of the QED. Finally, we present a review of the different determinations of the von Kitzling constant R) sub(K).Original Abstract: Nous presentons une revue des determinations les plus precises de la constante de structure fine alpha qui sont obtenues dans differents domaines de la physique. Nous decrivons la mesure du rapport h/m sub(Rb entre la constante de Planck et la masse de lmodifier letter apostropheatome de rubidium qui conduit a une valeur de alpha tres precise et tres peu dependante de lmodifier letter apostropheelectrodynamique quantique. Finalement nous presentons une revue des differentes determinations de la constante de LLLKitzling R) sub(K).
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